1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device, and more particularly, relates to a structure of a package of a high-frequency semiconductor element such as a GaAs-FET as well as to a method of manufacturing the semiconductor element.
2. Background Art
In a semiconductor package utilized in a high-frequency band, more particularly the C-band or the Ku-band, a substance such as epoxy resin having a large dielectric constant comes into close contact with a semiconductor chip within a commonly-used mold package, thereby introducing parasitic capacitance and deteriorating the characteristics of the semiconductor package. To prevent such parasitic capacitance, a package having a hollow cavity is commonly used for encapsulating the semiconductor chip so that the air surrounds the top surface of the semiconductor chip.
In contrast with the commonly-used transfer mold package, the hollow package involves the following disadvantages and hence suffers negative aspects in terms of productivity and costs.
First, when packages are transported as separate pieces, the packages must be frequently rearranged in different layouts during assembly/test processes.
Further, when a carrier belt is used for transporting the packages, the packages may be brought into random arrangements upon undergoing very small physical shock. Further, in the case where the carrier belt is used for transporting the packages, there is a limitation on the number of packages processed by an automatic machine, thus deteriorating productivity of the semiconductor package.
Second, as is likely to be the case with a lead frame, separate packages are brazed to a metal frame through use of a brazing filler material of Ag in order to improve productivity, so that the packages are brazed so as to assume the structure of a commonly-used mold-type lead frame. In this case, however, brazing adds to the manufacturing costs. Further, even in terms of productivity, the separate packages must be individually sealed in the course of a sealing process. Thus, the hollow package is inferior in productivity to the mold package.
The present invention has been conceived to solve the problem in the background art, and the object of the present invention is to provide a method of manufacturing a semiconductor device encapsulated in a hollow package, which method prevents deterioration of the high-frequency characteristics of the semiconductor device while ensuring the same productivity and costs as achieved by the mold package.